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Home  >  Journal list  >  Journal of the Ceramic Society of Japan  >  Vol.117  No.1364 (April) (2009)  >  pp.445-448

Journal of the Ceramic Society of Japan
<<Previous article Vol.117  No.1364 (April) (2009)   pp.445 - 448 Next article>>

Preparation of pore gradient silicon nitride ceramics by a high-velocity oxy-fuel spraying technique

Fei CHEN1), Qiang SHEN1), Julie M. SCHOENUNG2) and Lianmeng ZHANG1)
1) State Key Lab of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology
2) Department of Chemical Engineering and Materials Science, University of California Davis


  The preparation of pore gradient silicon nitride (Si3N4) ceramics was investigated by thermally spraying dense Si3N4 coatings onto the porous Si3N4 ceramic substrates via a high-velocity oxyfuel (HVOF) spraying method. Spray powders with excellent processability were developed and produced by spray drying and sintering in a nitrogen atmosphere. After sieving, the powders with average particle size of 45-75 μm were selected. Optimization of spray parameters such as spray distance and hydrogen flow rate was carried out in order to find the most decisive factor necessary for the production of dense and well-adhering coatings and pore gradient stuctures. Zirconium phosphate bonded Si3N4 porous ceramics were used as the substrate and coatings were obtained only when spray distance was 200 mm. A pore gradient structure was obtained at lower H2 flow rate, while poor-adhering coatings were obtained at higher H2 flow rate due to the etching. The hardness is significantly improved after Si3N4 coatings were successfully applied.


Keyword:
Silicon nitride, Pore gradient, High-velocity oxyfuel (HVOF), Spraying

Received: December 01, 2008
Accepted: February 19, 2009 , Published online: April 01, 2009
Copyright (c) 2009 The Ceramic Society of Japan

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